Hydraulic damper

Abstract

A hydraulic damper (2) includes a first piston body member (233), a second piston body member (234), a third piston body member (235), and a compression stroke disc assembly (231) compressed at a radially inner side thereof between the first (233) and said second (234) piston body members. The hydraulic damper includes a rebound stroke disc assembly (232) compressed at the radially inner side thereof between the second (234) and third (235) piston body members, and the compression stroke disc assembly (231) additionally includes an annular supporting member (2319) positioning discs (2311-2318) of the compression stroke disc assembly (231) at radially inner side thereof, while a radially inner axial passage (23191) is defined at the radially inner side of the supporting member (2319).

Claims

1. A hydraulic damper (2), in particular a motor vehicle suspension damper comprising a tube (22) filled with working liquid, a piston rod (21) led outside the tube through a piston rod guide and a piston assembly (23) disposed slidably inside the tube (22) dividing the tube into a compression chamber (25) and a rebound chamber (24) and comprising: a first piston body member (233) provided with at least one radially inner axial passage (2331) and at least one radially outer axial passage (2332); a second piston body member (234) provided with at least one radially inner axial passage (2341) and at least one radially outer axial passage (2342); a third piston body member (235) to compressively secure the piston assembly (23) to the piston rod (21); a compression stroke disc assembly (231) compressed at the radially inner side thereof between said first (233) and said second (234) piston body members, deflectably covering said at least one radially outer axial passage (2342) of the second piston body member (234) and provided with at least one radially inner axial passage in fluid connection with said at least one radially inner axial passage (2331) of the first piston body member (233) and said at least one radially inner axial passage (2341) of the second piston body member (234); and a rebound stroke disc assembly (232) compressed at the radially inner side thereof between said second (234) and said third (235) piston body members, deflectably covering said at least one radially inner axial passage (2341) of the second piston body member (234); wherein said compression stroke disc assembly (231) additionally comprises an annular supporting member (2319) positioning the discs (2311-2318) of said assembly (231) at radially inner side thereof, while said radially inner axial passage (23191) is defined at the radially inner side of said supporting member (2319).

2. The hydraulic damper according to claim 1, wherein said annular supporting member (2319) has a form of a sleeve abutting said first piston body member (233) or said second piston body member (234).

3. The hydraulic damper according to claim 1, wherein said annular supporting member (2319) has a form of an annular projection of said first piston body member (233) and/or said second piston body member (234).

4. The hydraulic damper according to claim 1, wherein said compression stroke disc assembly (231) and/or said rebound stroke disc assembly (232) is/are provided with openings (23162, 23182; 23211) at their deflectable sides.

5. The hydraulic damper according to claim 1, wherein said at least one radially outer axial passage (2332) of said first piston body member (233) has a form of an annular channel between the circumferential surface of said first piston body member (233) and the inner surface (221) of the tube (22).

6. The hydraulic damper according to claim 1, wherein the hydraulic damper is a mono- or twin-tube damper.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The exemplary embodiments of the present invention are presented below in connection with the attached drawings on which:

(2) FIG. 1 schematically illustrates a front right motor vehicle suspension;

(3) FIG. 2 is a schematic cross-sectional view of a fragment of a hydraulic damper according to the state of art;

(4) FIG. 3 is a schematic cross-sectional view of a fragment of a piston assembly shown in FIG. 2;

(5) FIG. 4 is a schematic cross-sectional view of a fragment of an embodiment of a piston assembly according to the present invention;

(6) FIG. 5 is a schematic exploded view of the piston assembly shown in FIG. 2 and FIG. 3;

(7) FIG. 6 is a schematic exploded view of the piston assembly according to the present invention shown in FIG. 4;

(8) FIG. 7 is a cross-sectional perspective view of the piston assembly shown in FIG. 4 and FIG. 6; and

(9) FIG. 8 is schematic cross-sectional view of a fragment of another embodiment of a piston assembly according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(10) FIG. 1 schematically illustrates a fragment of an exemplary vehicle suspension 1 attached to a vehicle chassis 11 by means of a top mount 12 and a number of screws 13 disposed on the periphery of the upper surface of the top mount 12. The top mount 12 is connected to a coil spring 14 and a rod 21 of a mono- or twin-tube hydraulic damper 2. Inside a tube of the damper 2 a piston assembly attached to the rod 21 led outside the tube is slidably disposed. At the other end the damper tube is connected to the steering knuckle 15 or a swing arm supporting the vehicle wheel.

(11) A hydraulic damper 2 shown in part in FIG. 2 is an example of a mono-tube damper that may be employed in a vehicle suspension 1 presented in FIG. 1 which comprises a schematically depicted movable piston assembly 23 known from the state of art having two separate mechanisms of generating damping force in dependence of the velocity of the piston rod.

(12) The piston assembly 23 makes a sliding fit with the inner surface 221 of the tube 22, dividing the tube 22 into a rebound chamber 24 (above the piston assembly) and a compression chamber 25 (below the piston assembly).

(13) At one end the piston rod 21 passes through and is secured to the piston assembly 23. The other end of the piston rod 21 is led axially outside the damper 2 through a sealed rod guide (not shown). The piston assembly 23 is provided with compression 231 and rebound 232 valve assemblies to control the flow of working liquid passing between the rebound chamber 24 and the compression chamber 25 while the piston is in movement. At the compression end, the tube 22 is closed by the floating gas cup assembly 26 for pressure compensation.

(14) The term “rebound” as used in this specification with reference to particular elements of the damper means these elements or these parts of particular elements which point toward the piston rod or in a case of a flow direction of the working liquid it refers to this flow direction that takes place during the rebound stroke of a damper. Similarly the term “compression” as used herein with reference to particular elements of the damper means these elements or parts of elements which point in a direction opposite to the piston rod or in a case of a flow direction of the working liquid it refers to this flow direction that takes place during the compression stroke of a damper. Piston assembly 23 of FIG. 2 is shown in detail in FIG. 3 and FIG. 5. It comprises first piston body member 233 in a form of a retainer, a compression stroke disc assembly 231, a second piston body member 234 provided at the circumferential surface thereof with an annular sealing 2343 made of Teflon material, a rebound stroke disc assembly 232 and a third piston body member 235 having in this embodiment a form of a washer 2351 and a nut 2352 screwed on an external thread made at the end of a narrower cylindrical portion 211 of the piston rod 21 and compressively securing all the elements of the piston assembly 23.

(15) The first piston body member 233 and the second piston body member 234 are provided with eight equiangularly disposed and aligned axial passages 2331 and 2341 (cf. FIG. 6). Furthermore the second piston body member 234 is provided with eight equiangularly disposed separate axial passages 2342 radially external with respect to the axial passages 2341. The first piston body member 233 defines an annular passage 2332 between the circumferential surface thereof and the inner surface 221 of the tube 22.

(16) The compression stroke disc assembly 231 is compressed at the radially inner side thereof by the force exerted by the nut 2352 between the first 233 and the second 234 piston body members, deflectably covering axial passages 2342 of the second piston body member 234.

(17) Similarly the rebound stroke disc assembly 232 is compressed at the radially inner side thereof between the second piston body member 234 and the retainer 2351 of the nut 2352, deflectably covering axial passages 2341 of the second piston body member 234.

(18) Discs of the compression stroke disc assembly 231 and the rebound stroke disc assembly 232 have differentiated widths and diameters to enable tuning of the damping force characteristic.

(19) For low speeds of the rod 21, during the compression stroke, working liquid flows from the compression chamber 25 to the rebound chamber 24 through two channels.

(20) The first channel is defined by the two passages 23211 of the disc 2321 of the rebound disc assembly 232, axial passages 2341 of the second piston body member 234, axial passages 23111-23181 of the discs 2311-2318 of the compression disc assembly 231 (cf. FIG. 5) and axial passages 2331 of the first piston body member.

(21) The second channel is defined by the passages 2342 of the second piston body member 234, twelve radial slots 23182 of the disc 2318 of the compression disc assembly 231 and the annular passage 2332 of the first piston body member 233.

(22) For low speeds of the rod 21, during the rebound stroke, working liquid flows through the first and the second channels defined above from the rebound chamber 24 to the compression chamber 25 but in the opposite direction.

(23) For low speeds of the rod 21 discs of the compression 231 or the rebound 232 disc assemblies do not deflect. They deflect after some rod velocity thresholds that may be tuned independently for a rebound and for a compression stroke. For this purpose it may be appropriate to provide disc valve assemblies 231 and 232 with slots, openings, unidirectional disc valves (e.g. disc with slots or openings covered by another disc) and various other means known to those skilled in the art.

(24) After reaching this compression stroke threshold, working liquid flows mainly through the second channel and the gap between the deflected discs of the compression stroke disc assembly 231 while during the rebound stroke, working liquid flows mainly through the first channel and the gap between the deflected discs of the rebound stroke disc assembly 232. Obviously both gaps open proportionally to the pressure of the working liquid with an increase of the damping force.

(25) Obviously in order to enable the flow of the working liquid through axial passages 23111-23181 of the discs 2311-2318 of the compression disc assembly 231, the discs 2311-2318 must be angularly aligned with each other which may create manufacturing, assembling and dimensional tolerance problems.

(26) FIGS. 4, 6, 7 illustrate an exemplary embodiment of the piston assembly 23a according to the present invention. The reference numerals corresponding to the same functional elements remain as in FIG. 3 and FIG. 5, with suffixes (a, b) added to distinguish particular embodiments of the piston assembly 23a and 23b.

(27) As shown, in this embodiment of the piston assembly 23a, the compression stroke disc assembly 231 additionally comprises an annular supporting member 2319 in a form of a sleeve. Radial flange 23193 of the sleeve 2319 is seated within the annular recess 2333 of the first piston body member 233 and supports the discs 2311-2316 of the compression stroke disc assembly 231. The annular ring 23192 of the sleeve 2319 serves to radially position the discs 2311-2316 and defines an axial passage 23191 of the assembly 231. Such a configuration excludes the necessity for angular orientation of the discs of the compression stroke disc assembly 231.

(28) FIG. 8 shows yet another embodiment of the piston assembly 23b made according to the principles of the present invention. In this embodiment the first piston body member 233 comprises a retainer 2335 and a slidable piston member 2334 that defines an annular passage 2332 between the circumferential surface thereof and the inner surface 221 of the tube 22.

(29) An annular supporting member 2319 for the discs of the compression stroke assembly 231 is defined by an annular projection of the slidable piston member 2334 of the first piston body member 233 so that radially inner axial passage 2331 of the first piston body member 233 and radially inner passage 23191 of the compression stroke disc assembly 231 form a single passage.

(30) The above embodiments of the present invention are merely exemplary. The figures are not necessarily to scale, and some features may be exaggerated or minimized. These and other factors however should not be considered as limiting the spirit of the invention, the intended scope of protection of which is indicated in appended claims.